The present invention relates to a submergible electrohydraulic drive unit for ramming and working devices to be used under water. More particularly, it relates to such a submergible electrohydraulic drive unit which has hydraulic pumps driveable by electric motors and connected with a pressure medium container, and flexible connecting conduits communicating the hydraulic pumps with a drive of the ramming or working device.
The units of the above mentioned general type are known in the art. U.S. Pat. No. 4,043,405 discloses a ramming arrangement with an impact body slidably guided in a housing, a drive piston connected with the impact body and slidably displaceable in a hydraulic cylinder-piston unit, and a drive unit connected with the hydraulic cylinder-piston unit via pressure medium conduits and a switching device. The drive unit has hydraulic pumps which are driven by an electric motor and a pressure medium container. The drive unit is displaceably upwardly and downwardly guided on the pressure medium cylinder-piston unit arranged on the upper end of the housing, through impact damping means. This known construction is recommended for ramming works under water. However, in this construction it is necessary to provide a shape which exactly corresponds to the upper end portion of the ramming device, and an impact damping displaceable guidance of the whole drive unit on the ramming arrangement.
For excavation of raw deposits located on or under the sea bottom respective underwater arrangements and constructions are to be installed in deep water. For this purpose various working devices must be used in considerable depths. It is always difficult to bring these devices with reasonable time and labor expenses to respective working locations underwater and to drive them with efficient operation. It is in principle possible to construct a special adjusted submergible electrohydraulic drive unit for each individual working device to be used in great water depths, and operate such drive units from a current source located above water through electrical supply conduits which lead to the working device under water with low energy loss, as compared with driving by the hydraulic medium through respective long conduits from a hydraulic pump over water. However, the lowering and subsequent withdrawal of each different device required for an underwater installation and their respective guidance in the working position even in favorable weather conditions requires considerable time and moreover must be performed by means of a respectively great number of underwater drive units adapted to respective working devices. This approach is actually at the limit of the efficiency of operation. This is even more true since the expensive and technically sensitive devices and drive units are formed for performing indispensible but in many times short time special works and then are no longer needed, so that they are stored for long time for the next occasion to use them.